So, she tries to track down the rest of the map while doing battle with her evil uncle (Frank Langella). (deseretnews.com)
The supposed leaked map for Red Dead Redemption 2 also depicts these locales, but at the southwestern corner, placing the rest of the map to the northeast of RDR's, meaning it would be more of an analogy for Louisiana, Arkansas and Alabama, a theory further supported by the swampy nature of the leaked map. (rdr2.com)
But any further speculation in this vein would risk giving away one of the novel's many plot turns, and so we leave the rest of the mapping to you! (bookbrowse.com)